@babel/plugin-proposal-class-static-block

NOTE: This plugin is included in @babel/preset-env, in ES2022

A class with a static block will be transformed into a static private property, whose initializer is the static block wrapped in an IIAFE (immediate invoked arrow function expression).

Example

  1. class C {
  2.   static #x = 42;
  3.   static y;
  4.   static {
  5.     try {
  6.       this.y = doSomethingWith(this.#x);
  7.     } catch {
  8.       this.y = "unknown";
  9.     }
  10.   }
  11. }

will be transformed to

  1. class C {
  2.   static #x = 42;
  3.   static y;
  4.   static #_ = (() => {
  5.     try {
  6.       this.y = doSomethingWith(this.#x);
  7.     } catch {
  8.       this.y = "unknown";
  9.     }
  10.   })();
  11. }

Because the output code includes private class properties, if you are already using other class feature plugins (e.g. `@babel/plugin-proposal-class-properties), be sure to place it before the others.

  1. {
  2.   "plugins": [
  3.     "@babel/plugin-proposal-class-static-block",
  4.     "@babel/plugin-proposal-class-properties"
  5.   ]
  6. }

Installation

  1. npm install --save-dev @babel/plugin-proposal-class-static-block

Usage

With a configuration file (Recommended)

  1. {
  2.   "plugins": ["@babel/plugin-proposal-class-static-block"]
  3. }

Via CLI

  1. babel --plugins @babel/plugin-proposal-class-static-block script.js

Via Node API

  1. require("@babel/core").transformSync("code", {
  2.   plugins: ["@babel/plugin-proposal-class-static-block"],
  3. });

References